Raman spectra of the graphyne-family: graphyne, graphdiyne and graphtriyne

Abstract

Graphyne-family materials, deriving from the insertion of acetylenic groups into graphene, are graphene allotropes and have been predicted to exhibit unique physicochemical properties that can be utilized for various applications. In this study, we used density functional theory to systematically investigate the structural, electronic, and Raman properties of the graphyne-family monolayers: graphyne (GY), graphdiyne (GDY), and graphtriyne (GTY). All the considered materials are confirmed to be dynamically stable and possess the same point group symmetry, resulting in similar Raman active phonons. The band gap, the number of Raman active modes with the same irreducible representation, and thus the corresponding Raman peaks increase with acetylenic units. Isotropic Raman intensities were observed under backscattering conditions, while distinct angular dependencies were noted for parallel incident light. In particular, unlike GY, the nonpolarized Raman spectra of GDY and GTY exhibit a similar pattern in which more pronounced Raman intensity is excited by a 633 nm laser than a 532 nm laser, which is understood to be an effect of their different light absorbance properties.